Abrasive wheel for form grinding



L. L. KATZENSTEIN.

ABRASIVE WHEEL FOR FORM GRINDING.

APPLICATION FILIED DEC.8. I917.

Patented Jan. 10, 1922.

W H N ME L N 0 E L WITNESSES UNITED STATES PATENT OFFICE.

LEON L. KATZENSTEIN', OF WORCESTER, MASSACHUSETTS, ASSIGNOR TO NORTON COMPANY, A CORPORATION OF MASSACHUSETTS. I

mm: wnnnr. ron. roan: GRINDING.

Specification of Letters Patent.

Application filed December 8, 1917. Serial No. 206,333.

9 '0 all whom it my concern:

Be it known that I, LEON L. KATZENSTEIN,.

a citizen of the United States of America, residing at Worcester, in the count of Worcester and State of Massachusetts, ave invented certain new and useful Im rovements in Abrasive Wheels for Form rinding, of which the following is a full, clear, and exact specification.

My invention relates to abrasive implements and more particularly to grinding wheels used for abrading, grinding or polishing various types of surfaces.

In the art of grinding, an abrading wheel is ordinarily made of abrasive grains or particles held together by a suitable bond, the grinding characteristlcs of the wheel depending not only upon the physical properties of the material being ground as well as those of the abrasive material, but also upon the nature of the bonding medium employed. This bond must be tough and hard so that it may hold the abrasive grain firmly under the strain and stress of the grinding operation until the cutting edge of the grain has been dulled and yet be of'such a nature that it may ultimately yield or break away and permit the dulled grain to be dislodged or fractured to present fresh cutting edges to the work.

The ordinary type of grinding wheel is of a cylindrical shape and the surface of revolution parallel with the axis of rotation of It is found in practice that the portions of the grinding face adjacent the edges of the wheel tend to wear away faster than does the intermediate portion, this being due to various causes but principally to the weak ness of the bond which holds the outermost abrasive particles only from the inner sides. This is particularly noticeable When the wheel is fed straight into the work as in grinding crank pins, or when it is necessary to grind up to a shoulder. Similarly, in grinding aform by means of a wheel having edges, projections, grooves or other shapes involving a change in surface curvature it is necessary that the wheel cut and wear away at substantially the same rate over its entire cutting surface to produce results true to-pattern. However, there is t1.

tendency for the more exposed ortions of the wheel to break down faster t an others, and espec1ally where a ridgeor an angular pro ectlon is provided on the wheel to cut a groove or angular shape in the object being ground. This excessive wear of the tion to overcome these. difficulties heretofore experienced in grinding and to provide an easily manufactured grinding wheel which is capable ofextensive use for grindmg forms, which will maintain the contour of its grinding surface during a normal grinding operation for a considerable life and yet be economical in use and capable of high production and which will have the characteristics of a relatively soft bonded wheel throughout the major portion of its grindingsurface but of a hard acting wheel at its corners orother locations of excessive wear.

With this and other objects in view, as will appear more fully in the following dis closure, my invention resides in the combination of parts and the steps of a process described .herein\ and covered by the appended claims.

In the accompanying drawings diagram matically illustrating my invention,

Figure 1 is a perspective view of a hard-- Patented J an. 10, 1922.

In the practice of my invention, I pro- 1 vide a uniformly wearing abrading surface for grinding implements, by adding to those parts of the wheel which are subject to excessive wear a filler having bonding, lubricating, elastic or other beneficial characteristics, which is capable of acting in con junction with and supplementing the primary bond with which the wheel was 1nitially made, to increase the life of such parts of the wheel and improve its cutting'action. I utilize for this purpose the porous structure inherent in the majority of grinding wheels, by impregnating a portion of the pores with a suitable filling material capable of adhering to the pore walls and of imparting greater strength, toughness, wear resistance or cutting ability to the wheel at the treated points.

As a specific embodiment of my invention, the structure and a method of making a reinforced vitrified or silicate wheel will be described, it being obvious that my invention in its broader aspects is applicable to and may be modified to include other Wheel structures. Assuming such a wheel to be of the usual cylindrical shape, subject to excessive wear or poor cutting action at its peripheral edges, I have illustrated in Figure 1 a simple construction involving a diskshaped Wheel 1, having its curved surface 2, as the grinding face, provided with side portions 3 and 4 so treated as to afford efficient grinding at the wheel corners, the longitudinal thickness of these portions being determined by the character of the grinding operations to be performed. These portions 3 and 4 extend diametrically from the surface 2 as far as the wheel will be worn away in grinding and preferably to the spindle aperture 5, and are separated by the untreated portion 6 of the wheel.

The vitrified or silicate Wheel is initially made according to well known methods,by molding in the desired form abrasive particles such as silicon carbide or crystalline aluminum oxide, mixed with a suitable nding medium such as clay or a silicate, after which the wheel is baked at a temperature suificient to fuse, vitrify or otherwise harden the bond.

Various materials may be selected for filling the pores of the wheel, depending upon the grinding characteristics desired. By way of example, I find it feasible to employ such materials as natural and artificial resins, including rosin, shellac or mixtures thereof, or the synthetic resins, known as bakelite, condensite, amberoid, plastic and fenoform, or rubber and the artificial substitutes therefor, or silicates, tars, pitches, asphalt, glue, oils, waxes, nitrocellulose or other cellulose derivatives, etc.

While the process of treating a previously made up wheel with one of these agents depends upon the chemical and physical properties of the materials, yet as a gen eral proposition it may be accomplished by impregnating the wheel with the filler in a melted condition or in solution, after which the wheel may be cooled or the solvent removed, as the case may be, and further necessary finishing operations such as bale ing employed to render the wheel fit for use. As a specific example involving the use of rosin or shellac, the bond is melted and the wheel, while hot, is impregnated with the molten material, as by spraying it onto the wheel faces, or by dipping the wheel, first one side and then the other, into the melt for a given period of time, until the pores shall have been impregnated to the desired depth. Any unnecessary excess of bond may be drained or otherwise removed from the pores and the Wheel allowed to cool. A subsequent baking operation in accordance with the general practice may serve to set the supplemental bond, preventing it from softening materially under the heat of a inding operation.

he extent to which a wheel should be impregnated with the filling agent depends upon the physical characteristics of the untreated, uniformly bonded wheel and of the work to be ground, it being obvious that care should be taken not to fill all of the pores or treat those portions of the wheel where the Wear is minimum, since if the wheel were completely filled it would then have a uniform bond over the entire grinding face and so wear or grind unevenly. It, however, should be noted that considerable latitude is afforded in the matter, due to the nature of the grinding operation; hence my claims are to be broadly construed in this light.

Since my invention does not depend upon the nature of the abrasive material or the size, shape or construction of the abrading grain,'it is obvious that the grain and grade of abradant may be selected as desired and that the abrasive grain may be uniform in size and character or in various combinations of desired materials and sizes. In accordance with my invention, I have provided a wheel which has its contours or other portions normally exposed to excessive wear so treated that the life of these wear able portions will be increased and the contour of the grinding surface of the wheel will be maintained for a longer life than the surface of an untreated wheel. Such a grinding wheel has the normal rapid cutting action of a wheel made of properly selected rain size and grade of bond strength throug out the major portion of its abrading surface, while its corners or other areas exposed to excessive wear have a different grinding action as if made of a bond of a harder grade and greater tenacity for holdinglthe abrasive grains in position.

aving thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A grinding wheel comprising a poroi1s,coherent body of abrasive grains bonded by ceramic material, the abrading surface of which has a section where excessive wear tends to occur, and a supplemental filler incorporated in the pore structure of such section which will tend to reduce such excessive wear and to maintain the relative contour of the abrading surface, the remainder of and forming abrading corners which act harder in their grinding characteristics than 10 does the intermediate unfilled surface portion.

Signed at Pittsburgh, Pennsylvania, this 30th day of November, 1917.

LEON. L. KATZENSTEIN. 

